JPH05263174A - Aluminum alloy for casting excellent in mechanical property - Google Patents

Abstract

PURPOSE:To provide secondary regenerated base metal as an alloy for aluminum for castings having high Fe content and suitable for the use for the important safety parts of transport apparatus and industrial machinary. CONSTITUTION:The objective alloy contains, by weight, 5.5 to 7.5% Si and 0.2 to 1.0% Mg, furthermore contains one or >=two kinds among 30 to 200ppm Sr, 30 to 200ppm Na and 15 to 100ppm Ca, and the balance Al with inevitable impurities, in which the content of Fe as the impurities is regulated to 0.3 to 0.6%, and moreover it contains 0.3 to 0.6% Cu.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for casting having excellent mechanical properties, which is used for transporting secondary recycled metal to transportation equipment,
Fe suitable for use in important safety parts such as industrial machinery
The present invention intends to provide it as an aluminum alloy for casting having a high content.

[0002]

2. Description of the Related Art Secondary aluminum recycled ingots are manufactured by collecting and remelting city scrap, but some of the iron inserts, screws, etc. assembled in the scrap are melted,
It is well known that the Fe content in recycled metal is high.

As described above, recycled aluminum ingots having a high Fe content are fragile and are unsuitable for use in important safety parts such as automobile wheels and suspension arms. It has been practiced to reduce the Fe content in recycled metal by adding high-grade primary metal with a low temperature.

[0004]

As described above, adding high-grade primary metal with a low Fe content naturally raises the price of recycled metal. Especially in recent years, Fe in recycled metal
However, since the amount of high-grade primary metal to decrease the Fe level to a general level has to increase at an accelerating rate, the merit of using recycled metal is very small. There is no choice but to be good.

On the other hand, in recent years, high-grade primary bullion has become a raw material that is difficult to obtain, and of course, due to economic reasons such as high price, the amount added to recycled bullion is also high. Inevitably, the Fe content in the recycled metal will increase, and its mechanical properties will inevitably deteriorate.In particular, the strength and elongation will decrease. There is no choice but to limit usage.

[0006]

Means for Solving the Problems The present invention has been studied to solve the problems in the prior art as described above, and secures strength and elongation even in an aluminum alloy having a high Fe content, and is an important safety member. The recycled metal as described above can be appropriately used, and is as follows.

(1) wt%, Si: 5.5-7.5%, Mg: 0.
2 to 1.0%, Sr: 30 to 200 ppm,
In an alloy containing any one or more of Na: 30 to 200 ppm and Ca: 15 to 100 ppm, the balance being Al and unavoidable impurities, and Fe as an impurity of 0.3 to 0.6% , Cu: 0.3-0.6%, an alloy for castings having excellent mechanical properties.

[0008]

The function of the elements contained in the present invention as described above will be described below. Si: 5.5 to 7.5% Si is an element that imparts fluidity to the alloy and, at the same time, coexists with Mg to obtain strength, and improves the filling property in the mold. If the amount is less than the lower limit, the effects are insufficient, while if it exceeds the upper limit, the elongation is reduced, which is not preferable for use in important safety parts and the like intended in the present invention. A desirable range is 6 to 7%.

Mg: 0.2-1.0% As described above, the strength can be obtained by heat treatment in the presence of Si. If it is less than 0.2%, the action is insufficient. On the other hand, if it exceeds 1.0%, it becomes easy to oxidize, causing the inclusion of oxides, increasing the amount of intermetallic compounds and affecting the strength and elongation,
The mechanical properties become unstable, so it should be 0.2-1.0%.

Fe: 0.3 to 0.6% Fe is an impurity that is inevitably contained in scraps and the like in recycled metal, and if it is less than 0.3%, the improvement according to the present invention is not necessary. On the other hand, when the amount exceeds the upper limit, the improvement effect of the present invention is lowered, and a large amount of Cu is required, resulting in deterioration of corrosion resistance and the like.

Cu: 0.3-0.6% It is intended to improve the deterioration of mechanical properties due to Fe in recycled ingots, etc., and below the lower limit value under the condition that Fe is 0.3% or more. The effect is insufficient. On the other hand, even if the content exceeds the upper limit, the improvement effect is lowered, and the corrosion resistance is deteriorated due to the increase of the Cu content.

One or two or more of Sr, Na and Ca. These elements refine eutectic Si and improve mechanical properties. Sr and Na are less than 30 ppm and Ca is 1 or less.
If it is less than 5 ppm, it is impossible to properly obtain those effects, while if Sr and Na are more than 200 ppm and Ca is more than 100 ppm, the fluidity is lowered, and there is a great possibility that the filling property in the mold is extremely impaired.

The alloy of the present invention as described above has a fast solidification rate and improves the mechanical properties due to the refinement of eutectic Si. Therefore, it is particularly suitable for die casting and heat treatment (T6 treatment). It is possible to exert excellent mechanical properties by applying. That is, the cast alloy of the present invention is subjected to a solution treatment by holding it at a temperature of 500 to 540 ° C. for 2 to 5 hours so that Si, Mg, and Cu are sufficiently solid-dissolved, and the treatment of the next step is also performed. Improves the mechanical properties.

Further, it is preferable to quench with water after the solution treatment as described above. That is, after quenching, 140-180
It is preferable to maintain the temperature of 3 ° C. for 3 to 7 hours for tempering to improve the mechanical properties. If the material is held at room temperature for about 12 hours (natural aging) after quenching and then tempered and then tempered, mechanical properties are further improved as compared with the case where no holding is performed.

[0015]

EXAMPLES Specific examples of the present invention are described below. (Example 1) The inventors of the present invention added Cu with various changes to an alloy having the composition shown in Table 1 below, melted the alloy by a conventional method, and cast it by a die.

[0016]

[Table 1]

The obtained alloys were heat-treated under the conditions shown in Table 2 below, and the tensile strength was measured. The results are shown in FIG. 1 when arranged in relation to the amount of added Cu.

[0018]

[Table 2]

That is, according to the results of FIG. 1, the tensile strength can be increased by 2 kg / mm ² or more by adding 0.2% or more of Cu to 26.5 kg / mm ² of the one without Cu. .3%
With the above, it is possible to increase by 29.5 kg / mm ² or more, and it is possible to increase to 0.
It was confirmed that there was a peak at about 5% and the improvement could be as high as about 5 kg / mm ² .

Example 2 The alloys of the present invention and comparative alloys having the compositions shown in Table 3 below were melted.

[0021]

[Table 3]

Each alloy is cast in a mold 535 after casting.
After holding at 3 ° C. for 3 hours, water quenching was performed, and tempering treatment was performed at 140 to 180 ° C. for 3 to 7 hours as shown in Table 4 below.

[0023]

[Table 4]

For each aluminum alloy obtained as described above, tensile strength (σ _B : kgf / mm ² ), 0.2%
The results of measuring the proof stress (σ _0.2 : kgf / mm ² ) and the elongation (δ%) are shown in Table 5 below.

[0025]

[Table 5]

That is, according to the results of Table 5, in Comparative alloys containing no Cu, Fe contains 0.3% or more, so that the mechanical properties are deteriorated as follows. On the other hand, it was confirmed that the alloys of the present invention to which Cu is added have high tensile strength and other mechanical properties even if Fe is as high as 0.35 to 0.45%. It was

[0027]

According to the present invention as described above,
A casting with high Fe content and excellent mechanical properties without reducing the Fe concentration by using a large amount of high-grade and expensive primary metal even under conditions where the Fe content is considerably high. Since it is possible to obtain the aluminum alloy for use and to appropriately manufacture the important safety parts by the secondary recycled metal in recent years, it is an invention having a great industrial effect.

[Brief description of drawings]

FIG. 1 is a table summarizing the relationship between Cu content and tensile strength in an aluminum casting alloy.

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[Procedure amendment]

[Submission date] April 24, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Example 2 A composition as shown in Table 3 below was used.
The present invention alloy having ~ And comparative alloys ~ Melt each
Made

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

Each alloy ~ 535 after casting in the mold
Hold at ℃ for 3 hours, quench with water, and see Table 4 below.
Una tempered at 140-180 ° C for 3-7 hours
Processing was carried out.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

That is, according to the results of Table 5, Cu should not be contained.
Comparative alloy that does not tighten ~ InFe content is low
As opposed toFe content of more than 0.3% ~
While the mechanical properties decrease like
The alloy of the present invention containing Cu Fe is 0.35 to 0.55%
High tensile strength etc.
It was confirmed to have the mechanical properties of

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (1)

[Claims] 1. At wt%, Si: 5.5-7.5%, Mg: 0.2-
1.0%, Sr: 30-200ppm, Na: 30-200ppm, Ca: 1
Contains one or more of 5 to 100 ppm,
The balance consists of Al and unavoidable impurities.
In an alloy with Fe of 0.3 to 0.6%, Cu: 0.3 to 0.6
% Aluminum alloy with excellent mechanical properties for casting.